Update `process_headers.zig` to use `@as`
Update `process_headers.zig` to use `@as`

raulgrell/zig,raulgrell/zig,andrewrk/zig,zig-lang/zig,raulgrell/zig,raulgrell/zig,raulgrell/zig,zig-lang/zig,andrewrk/zig,zig-lang/zig